Method of forming laminated cores for electrical apparatus



(No Model.)

A. SOHMID. METHOD OF FORMING- LAMINATED OORES FOR ELECTRICAL APPARATUS.

No. 406,858. Patented July 9, 1889.

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. UNITED STATES PATENT ()FFICE.

ALBERT SC I'IMID, OF ALLEGHENY, ASSIGNOR TO THE \VESTINGIIOUSE ELEC- TRIC COMPANY, OF PITTSBURG, PENNSYLVANIA.

METHOD OF FORMING LAMINATED CORES FOR ELECTRICAL APPARATUS.

SPECIFICATION forming part of Letters Patent No. 406,858, dated July 9, 1889.

Application filed May 13, 1889. Serial No. 310,599. (No model.)

T all whom it may concern: lation may be obtained and the proportion of Be it known that I, ALBERT SCHMID, a citiiron in the core correspondingly increased; zen of the Republic of Switzerland, residing but even with this form of insulation the non- 55 in Allegheny, countyof Allegheny, and State conducting material is usually found to ooof Pennsylvania, have inventedacertain new cupy about one-sixth as much space as the and useful Improvement in Method of Formiron. Another difficulty sometimes encouningLaminated Cores forElectrical Apparatus, tered in this construction is that the opera- (Case 319,) of which the following is a specition of stamping the plates formsa burr along 6 fication. the cut edges, and when the plates are placed 10 My invention relates to certain improvetogether the burrs areliable to piercethrough ments in the manufacture of cores for electhe sheets of paper, and thus destroy to a trical apparatussuch, for instance, as the greater or less extent the insulation between cores of electric inductoriums or converters, the different plates. The tendency of Fouthe cores of armatures for electric generators eault or eddy currents to circulate is usually 15 and motors, and other similar apparatus. greater near the conducting-wires than in the It has been found in practice that cores for body of the core, and therefore the presence electrical apparatus which are subjected to a of the burrs forming electrical connections rapid change of magnetic condition are more at the edges is the more objectionable. efficient and less liable to become heated The object of the present invention is to 20 when built of electrically-insulated laminae overcome these difficulties and to reduce to a of soft iron than when made solid. This is minimum the spaces occupied by the insuladue to the fact that in solid cores the electric tion, and at the same time to provide a method currents generated therein circulate within of manufacturing the core which will secure the same. Such currents, while of comparathe required insulation between the laminae, 25 tively low electro-motive force,are of considand shall also cheapen and improve the conerable quantity, and are liable to heat the struction of the core. core and render the apparatus less efficient. The invention consistsin first stamping from The use of laminated cores has, therefore, be sheets of suitable magnetizable materirlcome quite universal. In some instances the such as soft ironplates of the required size 0 adjacent laminae have been held apart by thin and form from which to build up the core; washers, leaving narrow air-spaces between then subjecting the plates to an annealing the laminze. In other instances thin sheets process, which is carried to such an extent of paper, fiber, or other non-conducting mathat a thin film of oxide is formed over their terial are placed between the laminae of soft entire surfaces, and over, also, the burrs or 3 5 iron. It is usually desirable that the mass of rough edges produced by the stamping pro- -iron in proximity to the coils of wire applied cess, and afterward building up the core by to a core should be as great as possible. The placing such plates side by side. presence of the insulation between the laminze The annealing process is carried on in the E lessens somewhat the amount of iron which following manner: The plates are arranged 40 is contained in a core of given size, and therein small piles in a suitable annealing-box.

fore tends to detract from the efficiency of The box is then placed in an oven and graduthe core. For this reason it is desirable that ally heated. This step in practice usually the insulation between the laminae should be occupies from six to twelve hours. hen the as thin as possible. The use of washers or proper temperature has been reached, it is 45 thin plates of insulating material is therefore kept approximately constant for a sufficient obj ectionable,because it requires a considertime to produce the required effects. This able separation of the successive plates. Anmay vary in different instances; but I usuother plan is to obtain theinsulation by pastally continue to so heat the plates for about rco ing very thin sheets of paper or other insutwelve hours. They are then allowed t o co 5o lating material to one surface of the sheets gradually, the heat being gradually lessened. of soft iron from which the laminae are after- This may occupy a somewhat greater length ward stamped. In this way very thin insuof time-say from twelve to twenty-fourhours.

The gradual cooling secures thoroughly-a1:- nealed soft plates. After this treatment the plates are found to be coated with a dark film or very thin scale. This scale consists chiefly of magnetic oxide. It is such a poor conductor of electricity as in effect to amount to an insulator, and at the samctime it is more or less magnetic, so that it serves, when the plates are placed together, not only to insulate them from each other, but also as a magnetizable material for the core, thus combining two desirable qualities. At the same time the insulation is extremely thin, and therefore allows the plates themselves to be brought into very close proximity. The thickness of the scale or film is found to be about two ten-thousamlths of an inch upon each surface, so that the core consists almost entirely of magnctizable material, and the plates themselves are separated the smallest possible distance. The oxide is very firmly attached to the surfaces of the plates and can only be removed by attrition, so that the plates may be handled without special care and without endangering the insulation.

It is desirable that the plates should be as soft as possible. As already stated, the annealing process has the effect of removing whatever temper may have been given to or remain in the plates, thus softening them and satisfying this requirement. The metal can not in practice be so perfectly annealed while in the form of large sheets from which the plates are stamped, as it is impossible to heat and cool them evenly; neither can it be thoroughly annealed before it is rolled into sheets, because the subsequent operation of rolling tends to harden it.

In the accompanying drawings, Figure l. is a side view of a plate employed in building certain forms of converters, such as described, for instance,in Letters Patent No. $66,345, issued July 12,1887, upon an application filed by me. Fig. 2 is a plan of a converterhaving a core of the characterdescribed. Fig. 3 illustrates an armature-plate, and Fig. i an armature-core composed of such plates.

Referring to Figs. 1 and 2,A represents the core of the converter of the construction which it is preferred to employ, and C C the primary and secondary coils, respectivcl y. The converter may, however, be constructed with a single coila portion of the length being designed to be connected in one circuit and a portion in another-01 a single coil may be connected entirely in one circuit. The core is composed of thin sheets or plates (1 of magnetizable mate1.-ial.-such, for instance, as soft iron. In preparing these plates rectangular plates are stamped with two holes c 6 and these holes are preferably of a rectangular shape and of such size as to receive the coils of wire. Each hole c c is cut open at f f These cuts f and may converge, as shown in the figure.

After the plates have been properly stamped their surfaces are oxidized, preferably by be ing placed in suitable vessels and gradually heated to a very high temperature. They are kept at such atemperature aproper length of time and then allowed to cool slowly. This step in the process has the double effect of thoroughly annealing and softening the met al and coating the surfaces with a thin film of magnetic oxide. This film also covers the edges and reduces the burrs prodncedby the stamping, covering them with an insulating material. In this manner the entire surface of each plate is sufficiently insulated to prcvent any considerable circulation of Ftuieault or eddy currents in the core. The plates are then placed one against another, their central tongues being inserted within the coils in the same general manner as describml in the patent beforereferred to, alternate plates being preferably inserted from opposite sides. The manner of building up the core and the shape of the plates may,lnnvcvcr, be matcrially varied without departing from thespirit of my invention.

Figs. 3 and 4; illustrate the construction of the cores of armatures for electric machines. The plates A are stamped as before, the shape and form being suited to the particular form of armature d esircd. 'lhey are then anneal ed and. thereby soften ed and coated by a ill in of i in sulatin g oxide, and afterward placed together side by side to form the complete armature core shown in Fig. -l:.

I desire to have it understood thatI do not limit my claims to the particular .forms of cores here described, nor to the precise periods of heating and cooling, llOl' tllO precise methods of oxidizing and annealing set forth in the above specification, and present them as being best suited to illustrate and disclose my invention.

In another application, filed November (3, 1888, Serial No. 290,150, I have described and claimed the cores themselves.

I claim as my in vention* 1. The hereinbefore-described method of constructing the cores of electrical apparatus, which consists in first stamping out plates of magnetizable material-such as soft ironafterward annealing and coating them with an insulating oxide, and building up the core from such annealed plates.

2. The hcrcinbcforc-described method of constructing the laminated cores of electric converters and. other electrical apparatus, which consists in first stamping out plates of ma-gnetizable material having the required shape and size, heating such plates after they are so stamped and allowing them to cool gradually, thereby covering their surfaces and edges by coatings of oxide, and aften ward building up the core from such plates by placing them face to face, substinitially as d escribed.

3. The hereinbeforc-described method of constructing the laminated cores of electric converters and other electrical. a paratus, which consists in first stamping thin plates IIO of magnetizable material having the required shape and size, heating such plates after they are so stamped and allowing them to gradually cool, thereby covering their surfaces and edges by coatings of magnetic oxide, and atterward building up the core from such plates by placing them face to face, substantially as described.

4. The hereinbeforc-described method of constructing the cores of electrical apparatus, which consists in first stamping out plates of magnetizable nmterial-such as soft ironafterward coating them with an insulating oxide, and building up the core from such oxidized plates.

5. The hereinbefore-described method of constructing the cores for electrical apparatus, which consists in first stamping out the plates of magnetizable material-such as soft ironafterward coating the edges of the same with an oxide, and building up the core from such oxidized plates.

In testimony whereof I have hereunto subscribed my name this 7th day of May, A. D. 1889.

1 ALBERT SClIMID.

\Vitnesses:

J. M. TATE, J r., W. D. UPTEGRAFF. 

